During takeoff, many aircraft have an engine thrust to aircraft weight ratio and a wing aspect ratio that generates a sufficient amount of lift to allow the aircraft to fly at a speed less than the actual takeoff speed. Nevertheless, most aircraft are unable to achieve liftoff until the actual takeoff speed is achieved because the sum of the nose down thrust couple and aircraft inertial moment about the main wheel axis exceeds the available, nose-up aerodynamic control moment.
Some proposals for allowing an aircraft to takeoff at a lower speed have included fixed length extensions incorporated into the nose landing gear system to increase a pre-flight angle of attack for the aircraft. However, some drawbacks of such a fixed length extension are that it increases the applied forces to the aircraft during landing and it requires more stowage space within the aircraft when retracted.
To address the aforementioned drawbacks, at least one hikeable and de-hikeable nose landing gear system has been developed. This system generally includes an upper cylinder attached to the aircraft and a piston/cylinder assembly coaxially mounted in the upper cylinder for moving the upper cylinder relative to a wheel assembly of the nose landing gear and in a direction that is substantially parallel to an upper cylinder axis. In this system, the free end of the piston-cylinder assembly is farthest from the aircraft and is coupled to the wheel assembly. A de-hiked, static configuration of the nose landing gear system includes the wheel assembly positioned at a first distance from the aircraft; whereas a hiked, static configuration includes the wheel assembly positioned at a second, and farther, distance from the aircraft. The static configuration is generally defined as when the aircraft is stationary (i.e., non-moving) with a weight of the aircraft respectively distributed on the nose and main landing gear systems.
A shock strut of the aforementioned hikeable and de-hikeable nose landing gear system may be lengthened or shortened by pressurizing the coaxially mounted piston-cylinder assembly. Thus before takeoff, the piston-cylinder assembly is pressurized, biased or otherwise actuated to lengthen the shock strut and increase the pre-flight angle of attack for the aircraft. After takeoff, the piston-cylinder assembly is actuated to shorten the shock strut before retraction of the nose landing gear system into a stowage compartment or nose landing gear bay.